1. Field of the Invention:
This invention relates to a semiconductor device, and more particularly to a semiconductor device having a multi-layered structure which permits a high density packaging by laminating semiconductor layers three-dimensionally into which semiconductor elements are fabricated.
2. Description of the Prior Art:
In light of the recent tendency of high integration of semiconductor elements, a study has been made to produce a single semiconductor device which permits a three-dimentional package of the semiconductor elements by laminating semiconductor chips or layers one upon another. In order to produce such a semiconductor device, problems inherent in its structure must be solved.
One of the problems is to form a semiconductor layer having crystallinity, which is sufficient enough to fabricate the semiconductor elements, upon an insulating layer for insulating between semiconductor layers. This is due to the fact that the semiconductor layer which is excellent in the crystalline state can not grow on the insulating layer deposited on a semiconductor substrate having irregular surfaces due to the formation of the semiconductor elements, because the insulating layer thus deposited is of no definite surface structure. Therefore, the semiconductor elements of superior characteristics can not be formed on the semiconductor layer deposited on such an insulating layer.
Another problem is how to insulate between the semiconductor layers and how to increase heat radiation characteristics of the semiconductor device. In general, a dielectric material is inferior in terms of heat transfer characteristics, and electrical insulation is inversely proportional to the heat radiation characteristics. Thus, the improvement of both the insulation and heat transfer characteristics makes it possible to enhance a degree of high integration and high density package of the semiconductor elements.
There are known two methods for laminating the semiconductors in three dimensions. One is to laminate element semiconductor wafers one upon another. The other is to form multi layers by thin film technology. Among these two methods, the thin film technology is appealing, because there is possibility of increasing the degree of the integration. However, conventional thin film technology is not effective to produce a semiconductor of excellent crystallinity and new developments have yet been put to practical use for producing such a semiconductor.
Thus, there still remains a need for a semiconductor device having good crystalline properties, excellent electrical insulation and heat radiation characteristics which can be produced with low cost materials.
Accordingly, it is an object of the present invention to provide a semiconductor device of multilayered structure which is excellent in the crystalline state and semiconductor characteristics.
It is another object of the present invention to provide a semiconductor device of multilayer three dimensional structure having excellent electrical insulation and heat radiation characteristics while permitting the fabrication of semiconductor elements in a high density arrangement in each of the semiconductor layers to remarkably increase the degree of integration of the semiconductor elements in the device.
It is still a further object of the present invention to provide a semiconductor device which can be produced at a low cost by using a substrate made of an inexpensive material, such as glass or the like.
Other objects, advantages and features of the present invention will become apparent to those skilled in the art from the following discussion and that following the description of the drawings.
Briefly, the foregoing and other objects are attained by providing a three dimensional semiconductor device which comprises a first semiconductor layer, a second semiconductor layer, and a beryllium oxide (BeO) film for insulating between the first and second semiconductor layers, wherein at least one of the semiconductor layers is grown on the BeO film to be regulated by a crystal structure of the beryllium oxide.
Having generally described the invention, a more complete understanding can be obtained by reference to the drawings which are provided herein for purposes of illustration only, and are not intended to be limiting unless otherwise specified.